* {
    margin: 0;
    padding: 0;
}

.PromptBox {
    position: absolute;
    top: 0;
    left: 50%;
}

.prompt {
    background: #000;
    color: #fff;
    margin: 10px auto;
    padding: 15px 50px;
    border-radius: 50px;
    /* 不可复制 */
    user-select: none;
    /* 当发生 改变 时过度 */
    transition: .5s;

    transform: translate(-50%);
    position: relative;
    top: -100px;
    opacity: 0;
}

.shown {
    top: 0;
    opacity: 1;
}